14 research outputs found
Tension in a Flat Belt Transmission: Experimental Investigation
No full textIn this paper we report the results of an experimental investigation aimed at determining the tension variation in a flat belt transmission. The belt tension was obtained by measuring its deformation with electrical resistance strain gauges. The investigation results are preceded by a reference to the belt transmission theory, in particular to Grashof's and Firbank's models. With regards to the Firbank model, in order to better interpret the experimental results, some original calculations were carried out starting from Firbank's paper.
The test results showed the efficiency of the Grashof model, as regards the presence of both an adhesion arc and a sliding one, which respectively decrease and increase with the growth of the force transmitted into the device and, at the same time, showed the Firbank model's validity in relation to the presence both of a shear strain and different sliding angles on the driving and driven pulleys
Experimental Study of a Squeeze Film Damper With Eccentric Circular Orbits
No full textAn experiment was carried out to investigate the distribution of oil pressure within a squeeze film damper. The damper was made so that its operation turned out to be as simple as possible, in order to highlight the main causes of practical deviation from theoretical prediction, with particular reference to cavitating mechanisms and regardless of inertia effects. The journal of the damper was given an eccentric orbital precession, with adoption of two distinct values of the offset. A groove placed laterally to the film secured the oil feeding. An outlet plenum at the opposite side of the film was operated with two different levels of exposure to the ambient air. Observation of the oil pressure was restricted to the film section midway between the inlet and outlet border, by means of three piezoelectric transducers plus a strain gage sensor. Theoretical prediction with a simple isoviscous short bearing uncavitated model was shown to be a significant reference for the experimental data. Analysis of the pressure levels and shape of the pressure waves made it possible to recognize operating conditions with the presence of tensile stresses and rupture of the film. The latter conditions were chiefly due to vapour cavitation. Spikes with tensile strength preceded in many circumstances the ruptured region. Air entrainment and its effects proved to be restricted at high frequency regimes with very low supply pressures and coexisted with vapour cavitation. The influence of moderate orbital distortion on pressure signals was highlighted. Significant differences in the pressure behaviour from one sensor location to the other, for the same operating conditions, were frequently observed
Grashof o Firbank? – Indagine Sperimentale su una Trasmissione a Cinghia Piana
No full textCon la presente ricerca sperimentale si intende esaminare come varia la tensione di una cinghia durante la trasmissione della potenza, allo scopo, in particolare, di verificare la validità della teoria di Firbank sul comportamento delle cinghie piane
Experimental Observation of Squeeze Film Damper Executing Offset Circular Whirl
No full textState-of-the-art knowledge about the squeeze film damper (SFD) has been pithily commented in a recent paper [1] putting in evidence the limits that still affect the application to practical cases, despite a sensible quantity of theoretical and experimental work that has been carried out in a long-lasting activity of research in the field [3, 4]. In particular, the heavy influence of film cavitation on SFD performances, with its very likely to set in character that affects most of the common operative conditions, still represents a strong motive for investigation. Many researchers have significantly contributed to clarify, among other aspects, the characteristics of film rupture within SFD (for instance [5, 6]). Recent work [7, 8] has stressed the importance of a common mechanism of cavitation that manifests with air ingestion in the film and consequent formation of bubbly-mixtures. In these conditions, the decaying damping forces can lower till to 15 percent of those pertaining to normal conditions in the absence of cavitation. Under these premises, an experimental work has been carried out about a damper executing offset circular whirl, in line with a previous investigation [2], focusing attention on waveform of pressure signals. Film rupture with vapor cavitation or gaseous cavitation, due to air suction, was observed. The former type was prevailing and frequently accompanied by a region with tensile stresses. Operating conditions with co-presence of both mechanisms of film rupture were also detected
